已知x²+y²=5,xy=2,求（2x²+xy+3y²)-(x²-xy+2y²)的值

已知x²+y²=5,xy=2,求（2x²+xy+3y²)-(x²-xy+2y²)的值
已知x²+y²=5,xy=2,求（2x²+xy+3y²)-(x²-xy+2y²)的值

已知x²+y²=5,xy=2,求（2x²+xy+3y²)-(x²-xy+2y²)的值
原式=2x²+xy+3y²-x²+xy-2y²
=(x²+y²)+2xy
=5+4
=9

原式=2x²+xy+3y²-x²+xy-2y²
=2(x²+y²)+y²+xy-x²+xy-2y²
=2(x²+y²)-（x²+y²）+2xy
=（x²+y²）+2xy=5+4=9